JP2001351585A - Alkaline battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve liquid leakage resistance in long-term storage under a high-humidity and high-temperature atmosphere in an alkaline battery provided with a sealing gasket having a thin safety valve. SOLUTION: As a material for the sealing gasket 7 fitted in the opening of a battery case 2, a polymer alloy consisting of a polyamide resin such as nylon 66 and polypropylene such as a block copolymer is used. In this way, a moisture absorbing amount is reduced while gas permeability is increased in comparison with a sealing gasket made of nylon 66, and heat resistance is improved in comparison with a sealing gasket made of polypropylene.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline battery using manganese dioxide as a positive electrode, zinc or a zinc alloy as a negative electrode, and an explosion-proof sealing gasket.

[0002]

2. Description of the Related Art FIG. 1 is a sectional view showing an example of an alkaline battery using an explosion-proof sealing gasket.

In this type of alkaline battery 1, FIG.
As shown in (1), a thin safety valve 7a is formed in the sealing gasket 7 in order to cope with the generation of excess gas due to misuse, and when the internal pressure increases, the safety valve 7a is broken by the internal pressure to remove excess gas. An explosion-proof structure for preventing the rupture of the alkaline battery 1 by discharging is provided.

Conventionally, as the sealing gasket 7, a material made of nylon 66 has been used in consideration of heat resistance, and a material made of polypropylene has been used in consideration of moisture resistance.

[0005]

However, in this case, there is a problem in the leak resistance of the alkaline battery 1 during long-term storage. That is, nylon 66 is easily affected by humidity, and in addition to causing dimensional deformation and a decrease in strength due to moisture absorption, since nylon 66 has extremely poor gas permeability, the internal pressure is rapidly increased due to excess gas. Alkaline battery 1
When stored in a humid atmosphere for a long period of time, the safety valve 7a of the sealing gasket 7 made of nylon 66 may break at a predetermined pressure or less and leak. On the other hand, since polypropylene has a low melting point and poor heat resistance, when the alkaline battery 1 is stored in a high-temperature atmosphere, the sealing gasket 7 made of polypropylene becomes weak due to heat and its safety valve 7a breaks below a predetermined pressure. There is a risk of causing liquid leakage.

The present invention has been made in view of such circumstances, and
An object of the present invention is to provide an alkaline battery having excellent resistance to liquid leakage during long-term storage in a high-temperature atmosphere.

[0007]

That is, the present invention relates to an alkaline battery (1) in which a sealing gasket (7) formed with a thin-walled safety valve (7a) is fitted into an opening of a battery case (2). It is constituted by using a polymer alloy composed of a resin and polypropylene as the sealing gasket.

Here, the composition ratio between the polyamide resin and the polypropylene in the polymer alloy is 9: 1 to 5:
It is preferable to be within the range of 5. Further, as the polyamide resin and the polypropylene in the polymer alloy, it is desirable to use nylon 66, nylon 6, a block copolymer, and a random copolymer, respectively. Further, the thickness of the safety valve is preferably set to 0.30 mm or less.

By adopting such a configuration, as compared with the sealing gasket made of nylon 66, the amount of moisture absorption is reduced and the gas permeability is increased, while the heat resistance is improved as compared with the sealing gasket made of polypropylene. Works.

It should be noted that reference numerals in parentheses are for convenience showing corresponding elements in the drawings, and therefore, the present invention is not limited to the description on the drawings. The same applies to the column of “Claims”.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an example of an alkaline battery using an explosion-proof sealing gasket.

The alkaline battery 1 has a cylindrical battery case 2 as shown in FIG.
A plurality (three in FIG. 1) of ring-shaped positive electrode mixtures 3 containing manganese dioxide and graphite as main components are inserted therein. A cylindrical separator 5 made of a nonwoven fabric is inserted into the internal space of the positive electrode mixture 3, and the separator 5 is filled with a gelled negative electrode 6 containing zinc as a main component. On the other hand, a beading portion 2b is formed near the opening of the battery case 2, and the sealing gasket 7 and the negative electrode terminal 9 are fitted on the beading portion 2b in an overlapping manner. A current collector 10 is mounted on the boss of the sealing gasket 7, and most of the current collector 10 is embedded in the gelled negative electrode 6. Further, a thin safety valve 7a is formed around the boss of the sealing gasket 7.

The sealing gasket 7 is formed using a polymer alloy composed of a polyamide resin (eg, nylon 66) and polypropylene (eg, a block copolymer). As a result, compared to the sealing gasket 7 made of nylon 66, the amount of moisture absorption is reduced and the gas permeability is increased. There is no fear that the liquid will break when the pressure is less than the pressure described above. Also,
Since the heat resistance is improved as compared with the polypropylene sealing gasket, even if the alkaline battery 1 is stored in a high-temperature atmosphere, there is no possibility that the safety valve 7a of the sealing gasket 7 breaks below a predetermined pressure and leads to liquid leakage.

To confirm this experimentally, 12 kinds of sealing gaskets made of different materials were experimentally manufactured, and an alkaline battery was assembled using these sealing gaskets, and various characteristics were compared. Table 1 shows the material of each sealing gasket and the thickness of the safety valve. In Table 1, the composition ratio between nylon 66 and polypropylene is a weight ratio.

[0016]

[Table 1]

<Hygroscopic Property of Sealing Gasket> First, in order to compare the hygroscopicity of the sealing gasket, six types of sealing gaskets were stored for 50 hours in a high humidity atmosphere at 60 ° C. and 90% RH. Changes in diameter and weight were measured. Table 2 summarizes the results. In Table 2, the dimensional change rate was calculated by subtracting the outer diameter before storage from the outer diameter after storage and dividing the difference by the outer diameter before storage.
Multiplied by 0%. The weight change rate is obtained by subtracting the battery weight before storage from the battery weight after storage, dividing this by the battery weight before storage, and then multiplying by 100%.
The sealing gaskets before storage were all stored at 40 ° C and 36 ° C.
It was vacuum dried for a long time to make it completely dry.

[0018]

[Table 2]

As is apparent from Table 2, the sealing gaskets containing polypropylene (Nos. 1-4, 10) were compared with the sealing gaskets consisting of nylon 66 only (No. 8).
Means that the rate of weight change is reduced,
The dimensional change rates of the sealing gaskets (Nos. 1 to 4) containing them also decreased. From this result, it was found that the water absorption decreased as the proportion of polypropylene in the sealing gasket increased.

<Operating Pressure of Safety Valve> Next, in order to compare the operating pressure of the safety valve when the sealing gasket is mounted on an alkaline battery, eight types of sealing gaskets were used at 60 ° C. and 90% R.
After storing for 50 hours in a high humidity atmosphere of H and absorbing moisture, the operating pressure of the safety valve in the high humidity atmosphere was measured.
Table 3 summarizes the results. The numerical values in Table 3 are relative values when the operating pressure of the safety valve is 100 when the sealing gasket is dried under vacuum conditions at 40 ° C. for 36 hours. Further, the operating pressure of the safety valve was measured in the same sealing gasket at a high temperature of 90 ° C. Table 3 also shows the results. The numerical values in Table 3 are relative values with the operating pressure of the safety valve measured in a room temperature (25 ° C.) atmosphere as 100.

[0021]

[Table 3]

As is clear from Table 3, the sealing gaskets (Nos. 1 to 4) containing 10 to 50% of polypropylene are:
Compared with other sealing gaskets (Nos. 8-11)
The operating pressure of the safety valve is 1 in high humidity and high temperature atmospheres.
Since the value is close to 00, stable operation of the safety valve can be expected even in a high humidity and high temperature atmosphere.

<Gas permeability of sealing gasket>
In order to compare gas permeability when the sealing gasket was mounted on an alkaline battery, the hydrogen gas permeability of six types of sealing gaskets was measured. Table 4 summarizes the results.
Shown in

[0024]

[Table 4]

As is evident from Table 4, the higher the proportion of polypropylene in the sealing gasket, the higher the hydrogen gas permeability. However, the sealing gasket (No. 10) in which the ratio of polypropylene was 5% did not differ from the sealing gasket (No. 8) consisting only of nylon 66.

<Storage Characteristics of Alkaline Batteries> Next, in order to examine the effect of the composition ratio of the sealing gasket on the storage characteristics of the alkaline batteries, eight types of alkaline batteries were heated at 60 ° C. and 90%
Thirty pieces were stored for 60 days in a high humidity atmosphere of RH and for 40 days in a high temperature atmosphere of 90 ° C. dry, and the presence or absence of leakage after storage was examined. Table 5 summarizes the results.

[0027]

[Table 5]

As is evident from Table 5, no alkaline battery using a sealing gasket (No. 1-4) containing 10 to 50% of polypropylene leaked after storage. It exhibited stable liquid leakage resistance even in an atmosphere. When the leaked alkaline battery was disassembled and investigated, the cause of the leak was all due to the operation of the safety valve.

In order to examine the effect of the type of polypropylene on the storage characteristics of an alkaline battery equipped with a sealing gasket containing polypropylene, two types of alkaline batteries were dried at 90 ° C. in a high-temperature atmosphere at 90 ° C. for 40 days. And stored for leakage. Table 6 shows the results.

[0030]

[Table 6]

As is apparent from Table 6, the composition ratio of nylon 66: polypropylene of the sealing gasket is the same (6
0:40), there is a difference in leakage resistance depending on the type of polypropylene, and the use of a random copolymer (N
o.5) uses homopolypropylene (No.7)
As a result, the result was excellent in liquid leakage resistance. When the leaked alkaline battery was disassembled and investigated, the cause of the leak was a crack in the sealing gasket.

<Appropriate Thickness of Safety Valve> Finally, for an alkaline battery equipped with a sealing gasket containing 10% of polypropylene, two types of alkaline batteries were used to examine the effect of the thickness of the safety valve of the sealing gasket on operating pressure. The working pressure of the safety valve was measured. Table 7 shows the results. Table 7
The numerical value in the middle is a relative value when the pressure resistance value of the sealing portion is set to 100.

[0033]

[Table 7]

As is clear from Table 7, when the thickness of the safety valve is 0.35 mm (No. 14), the operating pressure is 10
However, when the thickness of the safety valve was 0.30 mm (No. 13), the operating pressure was less than 100, indicating that the safety valve functioned perfectly. .

[0035]

As described above, according to the present invention, in the alkaline battery 1 in which the sealing gasket 7 in which the thin-walled safety valve 7a is formed is fitted in the opening of the battery case 2, it is made of polyamide resin and polypropylene. Since a polymer alloy was used as the sealing gasket 7,
Compared to a nylon 66 sealing gasket, the moisture absorption is reduced and the gas permeability is increased, while the heat resistance is improved compared to a polypropylene sealing gasket, so long-term storage in a high humidity and high temperature atmosphere The alkaline battery 1 having excellent resistance to liquid leakage at the time can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of an alkaline battery using an explosion-proof sealing gasket.

[Description of Signs] 1 ... Alkaline battery 2 ... Battery case 7 ... Sealing gasket 7a ... Safety valve

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H011 AA10 AA17 FF03 GG02 HH02 HH12 KK01 KK02 5H012 AA01 BB04 DD05 EE01 FF01 GG01 JJ10 5H024 AA03 CC02 CC14 DD04 EE09 HH01 HH13

Claims (5)

[Claims] An alkaline battery (1) in which a sealing gasket (7) having a thin safety valve (7a) formed therein is fitted into an opening of a battery case (2), wherein a polymer alloy comprising a polyamide resin and polypropylene is used. An alkaline battery used as the sealing gasket. 2. The alkaline battery according to claim 1, wherein the composition ratio between the polyamide resin and the polypropylene in the polymer alloy is in the range of 9: 1 to 5: 5 by weight. 3. The alkaline battery according to claim 1, wherein the polyamide resin in the polymer alloy is nylon 66 or nylon 6. 4. The alkaline battery according to claim 1, wherein the polypropylene in the polymer alloy is a block copolymer or a random copolymer. 5. The alkaline battery according to claim 1, wherein the thickness of the safety valve (7a) is 0.30 mm or less.